The present invention relates to an apparatus for direct airborne electromagnetic prospecting of hydrocarbons; for example, oil and gas deposits.
Specifically, it relates to an improved geophysical surveying system for transmitting and receiving many electromagnetic signals of varying frequency and orientation. The transmitting operation is carried out over several hundred combinations of transmitting system characteristics: helicopter altitude, electromagnetic field frequency and transmitter loop inclination and direction. The receiving operation multiplies the number of these combinations as two parameters, amplitude and phase, of three orthogonal electromagnetic field components H.sub.x, H.sub.y, H.sub.z, are measured by the receiving system. The transmitting and receiving operations are carried out first over a known area (a stage of system instruction) and then over an unknown area (a stage of actual prospecting). Moreover, a data processing system is provided that converts electronically the measured results directly into hydrocarbon occurrence probability levels on the basis of pattern recognition theory.